The assessment of fetal birth weight forms an important part of prenatal care. Therefore accurate early determination of fetal weight prior to delivery could markedly improving perinatal outcomes. Thus there is a need for a quick and easy method for estimating fetal weight in-utero particularly infants at risk of for either of the two extremes: (1) macrocosmia (also referred to as large for gestational age or LGA) or (2) small for gestational age (SGA) or intrauterine growth retarded (IUGR).
Currently the most reliable predictor of infant birth weight is ultrasonography where according to a recent review article it is capable of predicting birth weight to within 300 to 400 grams (Table 12, Nahum eMedicine Journal), but the authors cited that this as well as other techniques still have significant degrees of inaccuracy and suggested that a reasonable strategy for arriving at estimated fetal weight is still to use multiple estimates based on different sources of clinical and sonographic information. Moreover they noted that even with ultrasound, macrosomia is not easily predicted. Both ultrasonography and clinical palpation of fetal size have sensitivities of less than 60% for the prediction of macrosomia with false positives far greater than 40%. Likewise for small fetuses less than 1800 grams ultrasonic fetal weight estimates are often in error by as much as 25%. The disadvantages of ultrasonography include the complicated and labor intensive nature of the methodology that is often limited by the suboptimal visualization of fetal organs. It also requires costly equipment and highly trained personnel. The latter requisites often preclude use of any of current techniques in developing countries.
The use of ultrasound measurements of the fetus and information about the mother are combined to determine birth weight in WO2004/036359 published on 29 Apr. 2004.
Current American and Canadian guidelines recommend that all pregnant women be screened for gestational diabetes mellitus (GDM) between 24-28 weeks. Prior screening occurs only if multiple risk factors such as older maternal age, higher pre-pregnancy weight, membership in a high risk ethnic group or strong family history of diabetes exist or if previous diagnosis of GDM or delivery of macrosomic infant have occurred. However, several studies acknowledge that ‘selective screening’ based on these criteria can still result in under-diagnosis of GDM.
Current screening and diagnostic criteria for GDM are predicated on the observation that an abnormal oral glucose tolerance test (OGTT), with its accompanying gestational hyperglycemia, increases both perinatal and adult morbidity and mortality. It is argued that the increased flux of glucose across the placenta is the stimulus for the in-utero production of insulin from developing pancreatic islet cells and is the precondition for fetal hyperinsulinism, which in turn leads to increased fetal abdominal circumference, macrosomia, obesity and neonatal hypoglycemia and the diagnosis of GDM.